1. Field of the Invention
The present invention relates to a blow mold unit and a blow molding apparatus using the same.
2. Description of the Related Art
It is necessary to use a raised-bottom mold as a blow mold when forming a blow-molded container having a bottom that protrudes inward (e.g., dome-like bottom or free-standing bottle). A raised-bottom mold that is clamped to a pair of blow cavity split molds may be required separately from the pair of blow cavity split molds.
For example, two rows of blow molds that are secured in a back-to-back arrangement (see FIGS. 5 and 6 of JP-B-8-13501) may be used. When molding a container having a raised bottom using the two rows of blow molds disclosed in FIGS. 5 and 6 of JP-B-8-13501, a blow-molded container interferes with the raised-bottom mold and breaks if the raised-bottom mold is not removed before opening one of the pair of blow cavity split molds.
The raised-bottom mold may be moved upward and downward irrespective of the number of rows of blow molds from the viewpoint of ensuring molding quality (e.g., adjustment of the orientation or the thickness of the bottom). In JP-A-6-270235, the raised-bottom mold is moved upward and downward in order to ensure impact resistance upon falling or the like.
The pair of blow cavity split molds and the raised-bottom mold are closed in synchronization. However, a blow cavity mold closing/opening (clamping) device for the pair of blow cavity split molds and a driver device for the raised-bottom mold are provided independently. Therefore, when attaching or removing the blow mold to or from the blow molding apparatus, the pair of blow cavity split molds is attached to or removed from the blow cavity split mold closing/opening device, and the raised-bottom mold is attached to or removed from the raised-bottom mold driver device.
JP-B-4319863 discloses a rotary transfer blow molding apparatus that is configured so that a transfer plate that is intermittently transferred is moved upward and downward in an injection molding station that is one of a plurality of stations.
The blow mold includes a pair of blow cavity split molds and a raised-bottom mold that are attached to or removed from a different closing/opening device. Therefore, it is difficult to handle the pair of blow cavity split molds and the raised-bottom mold as an integral unit. This results in poor attachment/removal workability.
The blow cavity mold closing/opening device is disposed on the base of the blow molding apparatus, while the raised-bottom mold closing/opening device is disposed under the base of the blow molding apparatus. Therefore, it is troublesome to exchange the raised-bottom mold under the base when attaching or removing the blow mold to or from the blow molding apparatus.
The exchange work becomes more complex when using two rows of blow molds. For example, a mold closing/opening device that closes/opens two rows of blow molds performs a single-sided operation, and the blow molds are connected using a horizontal tie rod (see FIGS. 5 and 6 of JP-B-8-13501). This is because the blow molds cannot be slidingly transferred on the base of the blow molding apparatus when using the horizontal tie rod.